Methods and devices for creating security group and authentication over p2p network

A device for creating a security group over a P2P network, comprising:

• one or more invitee terminals each for attaching a public key to a peer advertisement, in which its own identification information is encrypted using its own private key, sending a resulting peer advertisement over the P2P network, and, when a group advertisement including group information about the security group is sent over the P2P network, decrypting the group advertisement using its own private key and participating in the security group using the group information;
• and
• an inviter terminal for searching for the peer advertisement to be sent over the P2P network, encrypting the group advertisement using respective public keys of the corresponding invitee terminals, and sending resulting group advertisements to the invitee terminals which the inviter terminal desires to invite to the security group.

A device for authenticating participation in a security group over a P2P network to which a group advertisement, including group information about the security group and a public key of an inviter party, is sent, the device comprising:

• one or more invitee terminals each for encrypting a propagation permission request message, together with its own signature, using the public key, and sending a resulting propagation permission request message so as to propagate a message within the security group;
• and
• an inviter terminal for decrypting the propagation permission request message using its own private key, authenticating whether the invitee terminal corresponds to a terminal invited by the inviter terminal, and, when the authentication is completed, sending a propagation permission response message to the corresponding invitee terminal.